This invention relates to aqueous ethylene/vinyl chloride/vinyl alkanoate and/or alkyl acrylate copolymer dispersions having a non-uniform particle size distribution, in which one particle size distribution maximum is at 0.03 to 0.2.mu. and a second maximum is at 0.15 to 1.mu. and in which 5% to 60% by weight of the particles belong to the amount of particles having said second maximum, as well as the method of production.
Previous processes for the manufacture of aqueous polymer dispersions have all been aimed at producing as uniform as possible a particle size distribution. As a rule of thumb, it can be assumed from German Published Application DE-OS No. 22 52 285, page 12, 2nd paragraph, that "the more the emulsifier is used, the finer are the particles." Furthermore, the desired particle size can be obtained by varying the emulsifier and protective colloid systems.
It is also known to produce dispersions with a low final concentration of dispersion auxiliaries by using seed latices. Frequently the amount of dispersion auxiliary required for the entire polymerization for the purpose of stabilization is introduced into the polymerization mixture through the seed latex. A disadvantage with this method, however, is the inadequate final stability of the dispersions (see DE-OS No. 21 41 864) and the frequently necessary long metering in times (6 to 18 hours). In addition, when using seed latices the particle size distribution is also substantially already predetermined.